This paper studies player incentives to invest in network reliability and security. We consider heterogeneous networked control system (NCS) - also called players - facing a class of problems involving discrete interdependent risks. We formulate the problem of security choices of the individual NCS as a non-cooperative two-stage game, in which players make they security and control decisions, respectively. We characterize equilibria of the game, thus determining the individually optimal security levels. The presence of interdependent security causes a negative externality, and the individual players tend to under invest in security relative to the social optimum. From our results, security and reliability decisions are tightly coupled, and should be considered jointly to improve efficiency.